1. Field of the Invention
The present invention relates to a composition for forming solar cell electrodes and solar cell electrodes fabricated using the same.
2. Discussion of Related Art
Solar cells generate electric energy using the photoelectric effect of a p-n junction which converts photons of sunlight into electricity. Front and rear electrodes are respectively formed on upper and lower surfaces of a semiconductor wafer or substrate with the p-n junctions in the solar cell. The photovoltaic effect at the p-n junction is induced by sunlight entering the semiconductor wafer, and electrons generated therefrom provide electric current flowing to the outside through the electrodes. The electrodes of the solar cell may be formed on the surfaces of the wafer by applying, patterning, and baking a composition for forming solar cell electrodes.
Methods of printing a composition for forming solar cell electrodes on the substrate may be largely classified into a gravure-offset printing method and a screen printing method. In the case of the gravure-offset printing method, the viscosity, drying properties and tackiness of the composition has a great influence, and in the case of the screen printing method, the rheological properties or thixotrophy of the composition is a large influence. Accordingly, it is important to use a composition for forming solar cell electrodes which may implement printed patterns with fine line widths and have a high aspect ratio when forming solar cell electrodes.
Korean Laid-Open Patent Publication No. 2011-0040713 discloses a method of controlling leveling properties and thixotropic properties of a composition for forming solar cell electrodes using a plasticizer to realize a narrow line width and a high aspect ratio. Korean Laid-Open Patent Publication No. 2010-0069950 discloses a technique of using a gravure-offset printing method in which a binder having a high glass transition temperature (Tg) is used as a second electrode to obtain a high aspect ratio, and Korean Laid-Open Patent Publication No. 2007-0055489 discloses a technique of improving a line width and aspect ratio by controlling thixotropic properties through a diameter of silver (Ag) powder. However, there is a limit to the above prior art for implementing fine line widths and high aspect ratio.